What’s done, is done.
—Shakespeare, Macbeth, Act 3, scene 2
If it isn’t tested, it doesn’t exist.
—Anonymous agile master
We recently transitioned to agile. But all our testers quit.
—Vignette from Crispin and Gregory 
As a sanity check in preparing for this chapter, I went to my bookshelf and looked at a number of texts on software requirements management, including my own [Leffingwell and Widrig 2003], for guidance on testing whether an application meets its requirements. Of course, I knew I wouldn’t find much on testing there, if for no other reason than I knew I hadn’t written much. I wasn’t surprised that other requirements authors haven’t ...